FAQ / Methodology
FAQ / Methodology
Data refreshed: 2026-05-17 · 511 counties analyzed · regenerated every 4–6 months
What is this?
An FA-anchored roof-permit coverage diagnostic — not a model feed. For every geography it answers one question: of the single-family homes on record, how many can we match to at least one indexed roof permit?
- Denominator — every First American (FA) single-family parcel in the geography.
- Numerator — those FA parcels matched to ≥1 BuildZoom roof permit.
- Coverage % — numerator ÷ denominator.
A low coverage number means "no permit data indexed here," not "no roof work happened." It is a data-availability map, not a market-activity map.
Which views can I trust?
| View | Reliability |
|---|---|
| By County (FIPS) | Reliable — the canonical spine. |
| By City (SitusCity) | Reliable — clean geography dimension. |
| By State | Reliable — county rollup. |
| By Municipality | Dirty — read with care. FA Municipality is fragmented (CITY OF X ↔ X), holds district/ward/school codes in some counties, and is null for ~2M SFH nationally. Quote only for counties with no MUNI_* flag, or use SitusCity. |
| Jurisdictions | BuildZoom's permit-issuing authority (AHJ) inventory + which AHJs fed the matched permits. |
Acceptance gate: INVARIANT_FAIL and JOIN_GAP must be 0 for numbers to be quotable.
Quality flags glossary
| Flag | Meaning |
|---|---|
CLEAN | No quality issue detected. |
HIGH_NULL_MUNI | Large share of SFH with a null Municipality in this county. |
MUNI_FRAGMENTED | Same place split across many municipality spellings. |
MUNI_DISTRICT_CODED | Municipality holds district/ward/school codes, not city names. |
JOIN_GAP | Master rollup and per-dimension sums disagree — must be 0. |
FA_COMPLETENESS_GAP | FA parcel coverage looks incomplete for the county. |
INVARIANT_FAIL | A structural invariant broke — must be 0, do not quote. |
How are jurisdiction names formatted?
BuildZoom's raw PERMIT_JURISDICTION is a coded string STATE_County[_City].
We render it readable:
FL_Orange→ Orange County (FL) (county-level AHJ)MN_Hennepin_Minneapolis→ Minneapolis — Hennepin County (MN) (city AHJ)
The raw code is kept as the link/URL key; the readable form is shown in tables.
Data sources
- First American — parcel / single-family universe (the denominator).
- BuildZoom — indexed building & roof permits (the numerator), with the permit-issuing jurisdiction (AHJ).
- Refresh cadence: full national rebuild every 4–6 months.
Full methodology: finding 73 in the project knowledge base.